Adding and Subtracting Fractions Lesson

Adding &

Subtracting

Fractions

A Review Lesson

Section 1: Add and Subtract Proper

Fractions

When adding or subtracting, there must
be a common denominator.
If the denominators are different:
(a) Write the problem vertically (top to
bottom)
(b) Find the LCD
(c) Change to equivalent fractions (by
building)
(d) Add or subtract the numerators
(leave the denominators the same)
(e) Simplify and reduce, if possible

Fill in the Blanks

What is the Least Common Denominator (LCD) of these fractions?

$\frac{1}{2}+\frac{5}{8}=$  

Multiple Choice

Find the difference:
$$\frac{3}{5}\ -\frac{1}{2}$$

• 2/5
• 1/10
• 1/5
• 1

Multiple Choice

Is this a correct answer?

• Yes, the student correctly added.
• No, you cannot add unlike denominators
• No, 5 + 7 is not 12
• No, 2 + 3 is not 5

Multiple Choice

Find the sum

• 12/17
• 17/20
• 20/17
• 2  1/2

Multiple Choice

$$\frac{3}{11}-\frac{1}{11}$$  

• $$\frac{3}{11}$$  

• $$\frac{4}{12}$$  

• $$\frac{2}{11}$$  

• $$\frac{1}{12}$$  

Multiple Choice

Once I have completed adding or subtracting fractions, I should always ____________ if possible.

• make equivalent fractions

• add again

• simplify

• multiply

Section 2: Adding and Subtracting Mixed Numbers

When adding or subtracting mixed
numbers, use the same procedure
for adding or subtracting fractions.
Note: Don’t forget to add or
subtract the whole numbers.

Multiple Choice

$$6\ \frac{2}{4\ }-2\ \frac{2}{5}=$$  
Reduce if needed.

• $$5\ \frac{2}{7}$$  

• $$4\ \frac{2}{20}$$  

• $$6\ \frac{1}{2}$$  

• $$4\ \frac{1}{10}$$  

Multiple Choice

$$3\ \frac{5}{8}\ +6\ \frac{1}{2}\ =$$  

Answer in simplest form.

• $$9\ \frac{1}{8}$$  

• $$9\ \frac{6}{8}$$  

• $$9\ \frac{9}{8}$$  

• $$10\ \frac{1}{8}$$  

Section 3: Subtraction with Regrouping

When mixed numbers cannot be
subtracted because the bottom
fraction is larger than the top
fraction, BORROW so that the
fractions can be subtracted from
each other.

Multiple Choice

$$4\ \frac{2}{5}\ -\ 3\ \frac{4}{5\ }\ =$$  

• $$\frac{3}{5}$$  

• $$1\ \frac{3}{5}$$  

• $$1\ \frac{2}{5}$$  

• $$\frac{2}{5}$$  

Multiple Choice

$$6\ \frac{1}{4}\ -\ 3\ \frac{2}{4\ }\ =$$  

• $$2\ \frac{3}{4}$$  

• $$3\ \frac{1}{2}$$  

• $$3\ \frac{3}{4}$$  

• $$2\ \frac{2}{5}$$  

Section 4: Addition and Subtraction of Fractions Word

Problems

Here are some KEYWORDS to look for in word problems:

●Sum, total, more than: mean to add

●Difference, less than, how much more than: mean to subtract

Multiple Choice

Daniel watched a beetle and a spider on the sidewalk. The beetle crawled 1/2 of a yard and the spider crawled 1/8 of a yard. How much farther did the beetle crawl than the spider?

• 1/4

• 3/8

• 1/2

• 5/8

Multiple Choice

Donny’s grandmother is making two recipes for Thanksgiving. The first needs  $$\frac{1}{4}$$    cup of flour and the second needs  $$\frac{5}{9}$$  cup of flour. How much flour will Donny’s grandmother need to make these two recipes? 

• $$\frac{6}{13}$$  cups

• $$\frac{13}{36}$$  cups

• $$\frac{2}{3}$$  cups

• $$\frac{29}{36}$$  cups

Multiple Choice

Simply Frosted sold   $$6\ \frac{1}{4}$$   loaves of cinnamon bread, and  $$3\ \frac{1}{4}\$$  loaves of raisin bread.  How many loaves of bread did they sell all together?

• $$20\ \frac{5}{16}$$  

• 3

• $$1\ \frac{12}{13}$$  

• $$9\ \frac{1}{2}$$